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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 12 |
| 3 | 42 |
| 4 | 0 |
| 5 | -1872 |
| 6 | -12672 |
| 7 | 172368 |
| 8 | 4523904 |
| 9 | 0 |
| 10 | -1822818816 |
| 11 | -27025270272 |
| 12 | 717889277952 |
| 13 | 33841118158848 |
| 14 | 0 |
| 15 | -36760473537435648 |
| 16 | -836717934176796672 |
| 17 | 32958199117834518528 |
| 18 | 2237077674319512600576 |
| 19 | 0 |
| 20 | -4686406322165888889913344 |
| 21 | -143728876497857181683023872 |
[1,3,12,42,0,-1872,-12672,172368,4523904,0, -1822818816,-27025270272,717889277952, 33841118158848,0,-36760473537435648, -836717934176796672,32958199117834518528, 2237077674319512600576,0, -4686406322165888889913344, -143728876497857181683023872] |